“Look, the President needs to sell this to the American people, and Congress needs to be involved,” said Senator Bob Corker, chairman of the Senate Foreign Relations Committee.

Corker did not condemn the framework deal reached by Iran and major powers in Switzerland on Thursday after months of negotiations, but he cited concerns over inspection provisions and differing accounts from Washington and Tehran over what was actually agreed.

The Tennessee Republican said his committee will go ahead with a planned April 14 vote on legislation requiring President Barack Obama to submit a final nuclear agreement to Congress for review and approval. The deal reached last Thursday is supposed to be the framework for a final agreement to be struck by the end of June.

Corker told Fox News Sunday that he had backing from key Democrats for the bill, including New York Senator Chuck Schumer, a prominent Jewish lawmaker who is line to be the new Senate Democratic leader in early 2017. Israel has been strongly critical of the nuclear deal.

Corker acknowledged he did not know if backers of the legislation in the Senate would have the 67 votes needed to override an expected veto by Obama, who says passing the measure would undermine the negotiations with Iran.

“I don’t know if we have 67 votes. … We have 64 or 65 that we are aware of today. There are many more that are considering this,” Corker said.

Many do not trust Iran and fear the verification measures are not adequate and face energetic lobbying by Israel, whose Prime Minister, Benyamin Netanyahu, says the deal as currently configured threatens his country’s security.

While many Democrats are skeptical of Iran, they may be unwilling to hand the U.S. president a major foreign policy defeat.

“Wavering Senate Democrats have been circumspect about the deal reached in Switzerland,” said Daniel Harsha, a former Democratic staffer on the House Foreign Affairs Committee.

Until the agreement is finalized and Secretary of State John Kerry testifies about it on Capitol Hill, “you aren’t likely to see many Senate Democrats, even those who have publicly backed new sanctions legislation … publicly pan the agreement,” said Harsha, now at Harvard University’s Kennedy School.

The agreement reached in Lausanne, Switzerland, would ease economic sanctions on Tehran in return for strict limits on its nuclear sites, centrifuges that can enrich uranium, and enriched uranium stockpiles.

Both Corker and Senator Lindsey Graham, a South Carolina Republican, previewed another possible Republican strategy.

If the final agreement with Iran is flawed, they argued, it would be better to keep in place an initial interim deal reached with Iran in November 2013, which contains limits on Tehran’s ability to enrich uranium that could be used for a nuclear weapon. All sides believe that is being observed.

“That’s one way of looking at this program — keeping the interim deal in place that’s been fairly successful, and have a new crack at it with a new president,” Graham said on CBS’ Face the Nation program.

Even if this strategy were adopted by the United States, however, it was unclear how it would play with the five other powers engaged in the negotiations with Iran — Britain, China, France, Germany and Russia.